fix(workspace): keep the cursor in a block that turns into a code block

Converting via /code or ``` swapped the text field for the code editor's
and left the focus nowhere, so further typing triggered app shortcuts.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/features/workspace/OutlinerBlock.tsx

@@ -289,6 +289,20 @@ export const OutlinerBlock: React.FC<OutlinerBlockProps> = ({
     adjustHeight();
   }, [localContent, block.type, block.level, activeFocus, adjustHeight]);
 
+  // Turning the block into another type (slash menu, ``` or markdown shortcut) can swap the text field
+  // for a new one (e.g. the code editor); the cursor must stay in the block so typing goes on there
+  const refocusAfterTypeChangeRef = useRef(false);
+  useLayoutEffect(() => {
+    if (!refocusAfterTypeChangeRef.current) return;
+    refocusAfterTypeChangeRef.current = false;
+    const ta = textareaRef.current;
+    if (ta && document.activeElement !== ta) {
+      ta.focus();
+      const end = ta.value.length;
+      ta.setSelectionRange(end, end);
+    }
+  }, [block.type]);
+
   useEffect(() => {
     window.addEventListener('resize', adjustHeight);
     // The field can be measured while hidden (phone layout shows the editor only after selecting a note);
@@ -335,6 +349,7 @@ export const OutlinerBlock: React.FC<OutlinerBlockProps> = ({
         : undefined;
     setLocalContent(clean);
     localContentRef.current = clean;
+    if (cmd.type !== block.type) refocusAfterTypeChangeRef.current = true;
     flushDebounce(clean, {
       type: cmd.type,
       ...(langOverride !== undefined ? { lang: langOverride } : {}),
@@ -423,6 +438,7 @@ export const OutlinerBlock: React.FC<OutlinerBlockProps> = ({
     }
 
     if (typeOverride) {
+      refocusAfterTypeChangeRef.current = true;
       flushDebounce(val, {
         type: typeOverride,
         ...(langOverride !== undefined ? { lang: langOverride } : {}),
@@ -578,6 +594,7 @@ export const OutlinerBlock: React.FC<OutlinerBlockProps> = ({
         const resolvedLang = rawLang ? resolveLanguageId(rawLang) || rawLang.toLowerCase() : '';
         setLocalContent('');
         localContentRef.current = '';
+        refocusAfterTypeChangeRef.current = true;
         flushDebounce('', {
           type: 'code',
           lang: resolvedLang,